Effect of large deformation on creep property evaluation by small-specimen bending tests

For small-specimen bending creep tests, large deformation occurs inevitably when the specimen under a large load or a long creep time. In such a circumstance, the conventional method for creep property evaluation, which is based on the small deformation assumption, may fail to attain a sufficiently high accuracy. Three typical specimens including circular ring, three-point bending and cantilever-beam specimens, are therefore examined. Based on the limit load approach, a critical load method is proposed to control the large deformation effect. Analytical solutions of the critical loads of the specimens are derived. Finite element method is used to quantitatively assess the effect of large deformation. The results show that the predicted creep curves of all the three specimens are significantly affected by the large deformation. Creep properties can only be accurately regressed when the applied load is below the critical load. The critical loads calculated by finite element method agree well with the analytical solutions. Furthermore, the analytical solutions are validated by the experimental results. The effect of creep time on the critical load has also been discussed.